Neurogastroenterology and motility : the official journal of the European Gastrointestinal Motility Society
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Neurogastroenterol. Motil. · May 2015
Randomized Controlled TrialThe effects of morphine and methylnaltrexone on gastrointestinal pain in healthy male participants.
Opioid antagonists are increasingly used to abolish the gastrointestinal side effects of opioids. However, they can potentially interfere with local analgesia exerted via opioid receptors in the gut. Thus, in the current study we aimed to explore the effect of rectal morphine before and after blocking opioid receptors outside the central nervous system with methylnaltrexone (MNTX). ⋯ No peripheral analgesic effect of morphine was found. Methodological shortcomings may have contributed to the lack of peripheral analgesia and thus, a peripheral morphine effect on rectal pain cannot be excluded. On the other hand, the combination of MNTX and morphine exerted a local effect on rectal distensions and seems to improve analgesia.